Telecommunication performance of persons with hearing handicap in relation to speech reception threshold

This study is concerned with the ability of hearing-impaired persons to perceive speech via the telephone and in particular with the possible benefit gained by the use of different kinds of auxiliary equipment (receiver amplifier, extra watch receiver, hearing aid in telemagnetic or microphone position, so-called combined amplifier, and combinations of these). In 203 hard-of-hearing subjects, grouped according to the speech reception threshold (SRT) of the better ear, the efficiency of the devices under test was investigated at two different line attenuations, one representing a good telephone connection and one representing a rather poor connection. It is concluded that persons with a slight hearing impairment (SRT:0--25 dB in the better ear) are able to use the telephone without special devices. The same applies to the majority of those with moderate hearing impairment (SRT:30--45 dB). For persons having a more severe hearing loss, a telephone with a receiving amplifier, or the individual hearing aid combined with the ordinary telephone set, can largely compensate for difficulties experienced when using the telephone. To complete the experiments, the audibility of a number of telephone bells was assessed. The bell in the standard set had low audibility for all the investigated groups of persons. Some of the other sound sources offered somewhat less difficulty.